Stems 2-2.5 mm wide, margins denticulate. Spathes: keels denticulate; outer less than 2 times inner, basally connate 3.8-7 mm; inner 20-30 mm. Outer tepals 13-17(-20) mm; filaments bluish violet. 2n = 64, 96. Flowering late spring--summer. Moist meadows, stream banks; 0--2200 m; B.C.; Calif., Idaho, Mont., Oreg., Wash., Wyo. The few dodecaploid populations of var. idahoense in eastern Oregon are morphologically indistinguishable from the far more common octoploid plants.